Method of manufacturing pneumatic-tire treads



B. DARROW. METHOD OF MANUFACTURING PNEUMATIC TIRE TREADS.

APPLICATION FILED FEB 10, i919.

Patented Feb. 1, 1921.

\ uurreo s'rA'r es pareuromce BURGESfi DABRO'W, on AKRON, cine, Assmiroa me THE GOODYEAR TIRE e airmen; 1 COMPANY, 01? AKRON, UHIO, A CORPORATION OF OHIO.

mn'rnon or mnnuractrunine PNEUMATIC-TIRE ranians.

Specification of Letters Patent.

Patented Feb. 1, ioailj Original application filed. March 61, 1918, Serial No. 220,753. Divided and this application filed. remai To all to hem it may concern l ie it known that I, BURGESS Dannow, a citizen of the United States, residing at Akron, in the county of Summit and State 5 of Ohio, have invented new and useful provements in Methods of hlanufacturin Pneumatic-Tire Treads, of which the fol:

The prevalent practice in the inanui'ius ture of a pneumatic tire involves the essen' 2e tial steps of building the fabric carcass; applying the covering strips of rubber, which form the side walls, cushion and tread, (the breaker strip being applied in with the cushion) and curing.

hen a pneumatic tire is under load a. change in the carcass cross-sectional con. tour is produced and this changed contour varies constantly in each portion of the tire as bumps, ruts, etc, are encountered and passed over.

One of the results of this change in contour is a shearing action between the tread strip and fabric carcass. The shearing action of a pneumatic tire under load is most acute in the zones which are located at the outer portions of the side walls and include the edges of the breaker strip.

This shearing action between the tread and cushion frequently starts a crack adja- 40 cent the edge of the breaker, which gradually results in the failure of the tire through destruction of the union between the tread and carcass.

It is the function of the cushion strip in a pneumatic tire to guard against disunion or separation between the tread and carcass by taking up through its elasticity, the shearing action between these elements.

However, while the cushion is usually sutficiently elastic to take up by stretching and This application 1s a true and legal diviJ Without rupture, the shearing action between the fabric and the tread in all other portions of the carcass, it very frequently happens that elasticity of the cushion is not sufi'icient to take up, in the zones at the outer Serial No. 276,109.

portions of the side walls, the shearing ac-' tion resulting from unusual and sudden dis" tortion when the car is overloaded and an unusually severe shock is sustained.

When such a shock comes, the cushion is, by the shearing action, stretched in the zone of the breaker strip edge beyond its limit of elasticity and a breaking of the union be-w tween the tread and carcass occurs. This rupture develops as the tire continues in service and causes tread separation. i

As a means for overcoming the foregoing dii'liculties and rendering the tire less liable to tread separation, I propose by my presentinvention to adopt the following cxpedientm The painting of the fabric carcass orthe cushion in thezone of the breaker strip edge with graphite, soapstone, or the use of any other expedient which will prevent the cushion and tread from forming a unionin this zone during the cure.

Constructing a tire in this manner will permit the tread and carcass to freely .HXOVBP relatively to each other under the shearing action and no rupture can result since 110 union exists to be broken.

The above and additional objects of a similar nature, which will be hereinafter more specifically treated, may be ttCCDHlplished by such means as are illustratcdfln the acciunpanyiug drawings, described in the: following specification, and then more palticularly pointed out in the claims which are appended hereto and form a part of this. application. 10

With reference to the drawings, wherein there has been illustrated a preferred em; bodiment of the invention, and throughout the several views of which, similar reference numbers designate corresponding parts:

Figure 1 is a cross section of a pneumatic tire shown more or less in diagrammatic. form and illustrating the manner in which the union between the cushion strip and-the carcass is interrupted in the zone coinprek bending the edge of the breaker strip; and f:

Fig. 2 is a similar View showing the tire flexed. .1

In illustrating my invention 1 have shown a tire of a frequently encountered type,"

tread slab.

the carcass proper, (which is formed, of course, of a plurality of cord sheets or layers); 11 designates the tread cushion; 12 the side walls; 13 the breaker strip, and 14 the tread strip or slab.

After the carcass has been built up in any suitable manner from plies of fabric, a gum strip or thin sheet of rubber is applied to the outer surface, extending from the valley of one bead to the valley of the other. Suitable side wall covering strips of rubber applied either in slab form or in small strips, are next put in position and the tire is then ready to receive the cushion strip.

Relatively narrow zones upon the surface of'the now rubber coated fabric carcass are then painted or otherwise equivalently treated with soapstone or any other material which will prevent the cushion strip from uniting with the carcass when the tire is cured. These zones are located as indicated in the drawing at the outer part of each side wall and in most tires should be situated to comprehend the edge of the breaker strip 13.

' The cushion strip is then placed centrally on the crown of the tire and then stitched down upon the carcass in the usual manner.

In this connection it should be explained that the Width of this zone will vary according to the size of the tire, but the proportions in most instances will be found to make a zone of approximately the dimensions indicated in Fig. 1. After the cushion strip is placed in position over the fabric carcass thustreated, the tread is applied and the tire then cured in a mold, in a wrap or on an air bag, according to which method of curing is to be followed in finishing the type of tire being built.

In the following claims I use the term tread portion to indicate broadly the cushion, breaker strip and tread slab or strip (which latter I have in some instances designated as the tread proper).

Although I prefer, in View of the results of the experiments thus far completed, to paint or equivalent!y treatthe rubber cover of the fabric carcass, I desire it understood that I also contemplate by my present invention the painting of the cushion or the lVhat I- claim is:

1. The method of constructing pneumatic automobile tire casings which consists in painting or otherwise treating the tire carcass in zones located approximately at the j unction of the tread and sidewalls, to pro-- vent the forming during the curing process of either direct or indirect union between 2. The method of constructing pneumatic automobile tire casings which consistsin applying a film of non-vulcanizable material such as graphite, soapstone or varnish to the tire carcassin zones located approximately at the junction of the tread and sidewalls, to prevent the forming during cure of eithera direct or indirect union between the tread portion and the carcass in such zones, and

' subsequently curing the tire.

rect union between the tread and the carcass.

in such zones, and subsequently curing the tire.

4. The method of constructing automobile tire casings which consists in the following steps; first, building a carcass; second, applying a thin sheet of rubber to the carcass for the major portion of its exterior, painting or otherwise treating with a non-vulcanizable material the exterior of said rubber cover, in zones located at the approximate junction of thecentral third with the lateral two-thirds ofthe carcass; third, applying a cushion stock over the said rubber cover; fourth, applying a breaker strip to the said cushion: fifth, applying a tread slab and sidewalls to completely incase the carcass from head to bead; and finally vulcanizing the tire.

5. The method of constructing pneumatic tire casings which consists in treating portions of the side walls of an uncured tire carcass in zones adjacent the tread portions of the tire in such manner as to prevent a union between the treated portions of the tire in such zones, and subsequently curing the tire carcass.

6. The method of constructing a pneumatic tire casing which consists in covering portions of the uncured tire with a lubrieating material, wholly inclosing the portions so covered by subsequent layers of vulcanizable material, and curing the tire.

7. The method of constructing a pneumatic tire casing which consists in painting the portions of the uncured tire with a non-vulcanizable material, wholly inclosing the painted portions by subsequent layers of vulcanizable material, and curing the tire.

In testimony whereof I have hereunto signed my name in the presence of two subscribing witnesses.

v BURGESS DARROW.

Witnesses: L. M. HARTMAN, 'R S. Tnoomm, 

